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helper.go
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helper.go
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package passit
import (
"io"
"slices"
"strings"
)
type concatGenerator struct {
gens []Generator
sep string
}
// Join returns a Generator that concatenates the outputs of each Generator to
// create a single string. The separator string sep is placed between the outputs in
// the resulting string.
func Join(sep string, gens ...Generator) Generator {
switch len(gens) {
case 0:
return Empty
case 1:
return gens[0]
default:
return &concatGenerator{slices.Clone(gens), sep}
}
}
func (cg *concatGenerator) Password(r io.Reader) (string, error) {
parts := make([]string, len(cg.gens))
for i, gen := range cg.gens {
part, err := gen.Password(r)
if err != nil {
return "", err
}
parts[i] = part
}
return strings.Join(parts, cg.sep), nil
}
type repeatGenerator struct {
gen Generator
sep string
count int
}
// Repeat returns a Generator that concatenates the output of invoking the Generator
// count times to create a single string. The separator string sep is placed between
// the outputs in the resulting string.
func Repeat(gen Generator, sep string, count int) Generator {
switch {
case count < 0:
panic("passit: count must be positive")
case count == 0:
return Empty
case count == 1:
return gen
default:
return &repeatGenerator{gen, sep, count}
}
}
func (rg *repeatGenerator) Password(r io.Reader) (string, error) {
parts := make([]string, rg.count)
for i := range parts {
part, err := rg.gen.Password(r)
if err != nil {
return "", err
}
parts[i] = part
}
return strings.Join(parts, rg.sep), nil
}
type randomRepeatGenerator struct {
gen Generator
sep string
min int
n int
}
// RandomRepeat returns a Generator that concatenates the output of invoking the
// Generator a random number of times in [min,max] to create a single string. The
// separator string sep is placed between the outputs in the resulting string.
func RandomRepeat(gen Generator, sep string, min, max int) Generator {
if min < 0 {
panic("passit: min argument must be positive")
}
if min > max {
panic("passit: min argument cannot be greater than max argument")
}
n := max - min + 1
if n < 1 {
panic("passit: [min,max] range too large")
}
if min == max {
return Repeat(gen, sep, min)
}
return &randomRepeatGenerator{gen, sep, min, n}
}
func (rg *randomRepeatGenerator) Password(r io.Reader) (string, error) {
n, err := readIntN(r, rg.n)
if err != nil {
return "", err
}
return Repeat(rg.gen, rg.sep, rg.min+n).Password(r)
}
type alternateGenerator struct {
gens []Generator
}
// Alternate returns a Generator that randomly selects one of the provided
// Generator's to use to generate the password.
func Alternate(gens ...Generator) Generator {
switch len(gens) {
case 0:
return Empty
case 1:
return gens[0]
default:
return &alternateGenerator{slices.Clone(gens)}
}
}
func (ag *alternateGenerator) Password(r io.Reader) (string, error) {
gen, err := readSliceN(r, ag.gens)
if err != nil {
return "", err
}
return gen.Password(r)
}
type rejectionGenerator struct {
gen Generator
condition func(string) bool
}
// RejectionSample returns a Generator that continually generates passwords with gen
// until condition reports true for the generated password or an error occurs.
//
// The behaviour is unspecified if condition never reports true.
func RejectionSample(gen Generator, condition func(string) bool) Generator {
return &rejectionGenerator{gen, condition}
}
func (rg *rejectionGenerator) Password(r io.Reader) (string, error) {
for {
pass, err := rg.gen.Password(r)
if err != nil {
return "", err
}
if rg.condition(pass) {
return pass, nil
}
}
}
type sliceGenerator struct{ list []string }
// FromSlice returns a Generator that returns a random string from list.
func FromSlice(list ...string) Generator {
switch len(list) {
case 0:
return Empty
case 1:
return String(list[0])
default:
return &sliceGenerator{slices.Clone(list)}
}
}
func (sg *sliceGenerator) Password(r io.Reader) (string, error) {
return readSliceN(r, sg.list)
}
type fixedString string
// Empty is a Generator that always returns an empty string.
var Empty Generator = fixedString("")
// Space is a Generator that always returns a fixed ASCII space.
var Space Generator = fixedString(" ")
// Hyphen is a Generator that always returns a fixed ASCII hyphen-minus.
var Hyphen Generator = fixedString("-")
// String returns a Generator that always returns the given string.
func String(s string) Generator {
return fixedString(s)
}
func (s fixedString) Password(io.Reader) (string, error) {
return string(s), nil
}